Head-mounted display devices are electronic devices that use near-eye display technology to allow a user to see an enlarged virtual image. The head-mounted display device usually includes a housing, a display screen received in the housing, and a lens module matching with the display screen, which together constitute a display unit. An image beam emitted by the display screen is projected to the user's eyes by the lens module, thus allowing the user to see a virtual image. An existing head-mounted display device integrates a headphone, thus the user does not need an external earphone. When wearing the above-mentioned head-mounted display device, as the same manner as wearing the headphone, the user needs to pull two headphones open to increase a spacing between the two headphones and then wears the head-mounted display device to a head. During wearing, a portion of the display unit connected to the headphones is also deformed as the headphones are pulled open. In order to adapt to the above-described deformation, a peripheral of the outside housing of the display unit is designed to be similar to a head mounted structure of the head mounted headphone. However, this kind of head mounted structure is composed of a complete arc, thus a problem exists that a clamping force of the headphones to the user's ears is too large.